In process automation technology, field devices are often applied for registering and/or influencing process variables. Serving for registering process variables are sensors, such as, for example, fill level measuring devices, flow measuring devices, pressure and temperature measuring devices, pH-redox potential measuring devices, conductivity measuring devices, etc., which register the corresponding process variables, fill level, flow, pressure, temperature, pH-value, or conductivity. Actuators are for influencing process variables, as, for example, valves or pumps, via which the flow of a liquid in a section of pipeline, or the fill level in a container, can be changed. In principle, all devices, which are applied near to the process and which deliver or process process-relevant information are referred to as field devices. Besides the aforementioned sensors and actuators, units which are connected directly to a fieldbus and are for the communication with the superordinated units are generally also referred to as field devices, such as e.g. remote I/Os, gateways, linking devices and wireless adapters. A large number of such field devices are produced and sold by the Endress+Hauser-Group.
In modern industrial plants, field devices are connected with superordinated units, as a rule, via bus systems (Profibus®, Foundation® Fieldbus, HART®, etc.). Normally the superordinated units involve control systems, or control units, such as, for example, a PLC (programmable logic controller). The superordinated units are for, among other things, the process control, process visualizing, process monitoring as well as the start-up of the field devices. The measured values registered by the field devices, especially by sensors, are transmitted via the connected bus system to one or, in given cases, also to a number of superordinated unit(s). Along with that, a data transmission from the superordinated unit via the bus system to the field devices is also required; this is especially for the configuring and parametering of field devices or for diagnostic purposes. Speaking generally, the field device is serviced via the bus system from the superordinated unit.
Besides a hardwired data transmission between the field devices and the superordinated unit, there is also the opportunity for a wireless data transmission. Especially in the bus systems Profibus®, Foundation® Fieldbus and HART®, a wireless data transmission via radio is specified. Additionally, radio or wireless networks for sensors are specified in the standard IEUE 802.15.4 in greater detail. For implementing a wireless data transmission, newer field devices, especially sensors and actuators, are embodied partially as radio-field devices. These have, as a rule, a radio unit and an electrical current source as integral components. In such a case, the radio unit and the electrical current source can be provided in the field device itself or in a radio module connected durably to the field device. Through the electrical current source, an autarkic energy supply of the field device is enabled.
Along with that, there is the opportunity to equip field devices that do not have radio units—thus the installed base—with a radio-field device through the coupling with, in each case, a wireless adapter which has a radio unit. A corresponding wireless adapter is described, for example, in the publication WO 2005/103851 A1. The wireless adapter is, as a rule, releasably connected to a fieldbus communication interface of the field device. Via the fieldbus communication interface, the field device can transmit the data that is transferred over the bus system to the wireless adapter, which then transmits this via radio to the target location. Conversely, the wireless adapter can receive data via radio and forward it to the field device via the fieldbus communication interface. Supplying the field device with electrical power can occur via an energy supply unit of the wireless adapter.
In the case of autarkic radio-field devices and wireless adapters, the communication, for example, with a superordinated unit, is conducted as a rule via the wireless interface of the radio-field device or the wireless adapter. Additionally, such radio-field devices, or wireless adapters, have, as a rule, a hardwired communication interface. For example, in the HART-standard, it is provided that radio-field devices must also have, besides a wireless interface, a hardwired communication interface. Via such a hardwired communication interface, much is possible, for example, local configuration of the radio-field device, or of the wireless adapter, via a service unit, such as, for example, a handheld communicator that is connected to the hardwired communication interface. Additionally, the hardwired communication interface can be embodied as a fieldbus communication interface, so that communication is conducted corresponding to a bus system, such as, for example, one of the standardized bus systems Profibus®, Foundation® Fieldbus or HART®. Via such a fieldbus communication interface, the radio-field device, or the wireless adapter, can also be connected to a corresponding hardwired fieldbus.
The energy supply unit, or the electrical current source, of a wireless adapter or of a radio-field device is, for example, a battery provided in the wireless adapter or in the radio-field device, a fuel cell, a solar energy supply and/or a rechargeable battery.
In the installed base, the most varied of types of field installations are found: Many of the field devices are embodied as 4-20 mA field devices. Here the analog 4-20 mA-electrical current value represents the measured value. Additionally, a digital communication can be superimposed on the electrical current signal, which is usually based on the HART protocol, but it does not have to be. The term ‘field installation’ subsumes, besides the two-wire field devices, naturally also four-wire-field devices; furthermore, servicing devices fall under the term, which, for example, are used for parametering the wireless adapter, or also the application of the wireless adapter in modem operation.
A wireless adapter, which is designed at least for one protocol used in automation technology for digital communication, is usually tailored to the particular field installation. In the case of the known solution, the necessary flexibility to apply the wireless adapter to different field installations is missing. It is obvious that the conventional solutions to it, consequently, are implemented very complexly.